The present invention relates to an ink-jet recording apparatus for printing data on large-sized recording media using ink-jet recording heads and more particularly to an ink supply unit.
As an ink-jet recording apparatus is used to do a large quantity of printing by reciprocating recording heads in the width direction of recording paper while ink is supplied from ink supply sources to the recording heads, what is designed to do a large quantity of printing follows a method of supplying ink to recording heads via tubes connected to ink supply sources contained in a casing is followed.
Since such an ink-jet recording apparatus is so arranged as to generate ink drops by pressurizing ink in pressure generating chamber, the pressurizing force of the ink will lower if bubbles are contained in the ink, thus lowering the discharge performance of the ink drops as well. Consequently, it is necessary to supply ink containing no dissolved air to the recording heads.
For the reason stated above, ink which is sufficiently deaerated at factories, enclosed in ink cartridges or ink bags and packaged in air-insulated containers have been offered on a commercial basis.
In the case of an ink-jet recording apparatus for use in printing posters and the like using large-sized recording media, however, a large quantity of ink is consumed at the time of printing. Consequently, as shown in FIG. 5, there has been employed an ink cartridge as an ink supply means comprising a flexible ink bag A for enclosing deaerated ink, and an ink-end detecting plate B for operating an ink end detector in ink-near-end and ink-end conditions, the ink bag A and the plate B being contained in a casing C, C'.
The ink bag A is formed of an aluminum laminate film comprising two sheets of films, for example, an outer nylon film and an inner polyethylene film with aluminum foil as an intermediate layer in order to secure the gas barrier property. The ink bag A flexibly deforms in proportion to the quantity of ink without damaging the deaerated property.
However, it is necessary to increase the strength of the bag material needs increasing and increase the rigidity of the bag as the quantity of ink as well as the volume of the bag is increased. The increased rigidity of the ink bag makes it difficult to smoothly supply ink to recording heads when the quantity of ink exceeds with normally about 500 cc. In other words, there is a limit the size of such an ink bag.
Moreover, the ink supply needle of an ink supply tube is inserted into a septum E formed of an elastic material such as rubber formed at an ink supply port D and this allows air to penetrate into the ink supply passage when the needle is detached. In a case where the ink supply is depleted during the printing operation, there develops a problem arising from the fact that work efficiency is lowered because the task of refilling the recording heads with ink becomes necessary.
Another problem is that the operator of the ink-jet recording apparatus may replace the ink bag with a new one even though the remainder of the ink is plenty as an absolute quantity, but still not sufficient enough to print data to be printed, thus wasting ink, or perform an ink-refilling operation.